1. Fields of the Invention
The present invention relates to an isolator, especially to an isolator with compact volume for convenience of assembling, processing, and isolating interference caused by poor ground loop during signal transmission so as to improve impedance matching. Moreover, the device has better bandwidth flatness, lower insertion loss, and better return loss so that signals with better waveforms are obtained by the isolator.
2. Descriptions of Related Art
The CATV system with two-way communication ability uses coaxial cables (or optical cables) to deliver television signals from cable television companies with equipments, called the head end to end users' homes (subscriber end). The cable television or telecommunication system companies receive various sources of programs such as satellite signals, wireless signals or microwave signals of television stations or broadcast stations by different antennas or air self-produced programs. The various signals are processed by the equipments in the head end and then are sent to the users' end by cables. During the processes, various components with different functions such as filtering, amplification and distribution etc are used.
As shown in Taiwanese Pub. App. No. M244634, published on Sep. 21, 2004, a common isolator such as an RF (radio frequency) adaptor is revealed. The RF adaptor is disposed on a signal transmission device and is connected with a terminal with RF wire. The RF adaptor consists of a main body having an insertion hole corresponding to the terminal and a channel connected with the insertion hole, a transmit member located in the channel of the main body and transmitting the RF signals into the signal transmission device after being electrically connected with the inserted terminal, and an isolation member mounted in the channel. The isolation member includes a first capacitor on one end of the channel, a second capacitor on the other end of the channel, and an inductor connected serially between the first capacitor and the second capacitor. The transmit member inserts through the isolation member while the isolation member is for isolating noise except the signal from the terminal when the terminal inserts into the main body.
The above RF adaptor is disposed on a signal transmission device and is connected with a terminal with RF wire. However, in practice, the impedance matching of the device in the high-frequency passband is not good. Thus the higher the frequency is, the larger the loss of high frequency signal is. Therefore there is a need to improve the design and structure of the device.
In order to overcome above shortcomings, refer to Taiwanese Pub. App. No. M331765, a novel isolator is provided. The isolator includes a connector, a first ring capacitor, a second ring capacitor, and a circuit substrate assembled inside a housing. The insulation cover is inserted by a connector that is disposed with a plug-in unit. An assembling protrusion is arranged at the other end of the connector and a stopper is disposed around the connector. At least one iron core is disposed around the assembling protrusion of the connector. The front cover is connected with a fixing seat whose two ends are depressed to form a first space and a second space. A first ring capacitor and a second ring capacitor are respectively received inside the first space and the second space. A circular spring is arranged at one end of the first ring capacitor as well as one end of the second ring capacitor correspondingly. The other end of the fixing seat is connected with an outer tube that is mounted with a circuit substrate. A terminal portion with a plug-in unit mounted therein is arranged at an outer end of the outer tube.
In accordance with the structure mentioned above, the disadvantages of the RF adaptor are improved, the impedance matching of the device is improved and the device has better bandwidth flatness, lower insertion loss, and better return loss property. Thus signals with better waveforms are obtained.